Process of treating ferrous metal articles



Patented June 3, 1930 UNITED STATES PATENT oFF cr:

MARLIN 0. Julian AND WILBERT A. nmomn,

OF DETROIT, 'IICHIGAN, ASS IGNORE,

.BY MESNE ASSIGNMENTS, TO PARKER RUST PROOF COMPANY, OF DETROIT, MICHI- GAR, A CORPORATION OF MICHIGAN 'IROCESS OF TREATING FERROUS METAL ARTICLES No Drawing.

The present invention relates to the treat- '5 reference to increasing the rust resisting qualities of said articles.

Among the objects of the invention is a process in whichthe ferrous metal articles are provided with a rust proofing chemically adherent coating.

Another object is a process of rust proofing such articles in which the rust proofing coating is provided in a greatly reduced time of treatment.

Other objects will readily occur to those skilled in the art upon reference to the following description.

In the Patent No.- 870,937, issued to Coslett, Nov. 12, 1907, there is described a process in which phosphoric acid is used to treat the surface of ferrous metal artic es in order to provide on such articles a coating of phosphatic materialf, which coating adheres strongly to the sur ace and is apparently chemically united therewith. This phosphatic coating is highly resistant to rust and protects the metal from oxidation.

In the practicing of the Coslett process and of various modifications which have since been made, it has been found necessary to treat the articles in these solutions and to leave them under such treatment for considerable time so that rust proofing by these various processes requires a period of several hours.

It has been found that this period may be reatly shortened by the modlfication herelnafter described and in fact, the time is decreased to approximately one third or less of the time required with t e Coslett process.

It has been found that by heating the suitably cleaned articles to within a rather narrow temperature range and immersing them, while still heated, in a solution prepared according to the Coslett process and retaining them in the solution for only a very short period, after which they are removed and baked at about the same temperature, as or slightly higher than that of the preheating step, that a protective coat will be formed on the arti- Appllcation filed June 30, 1928. Serial No. 289,818.

cles, which coating compares very favorably with thecoatings produced by the more coinplicated and extended processes.

In carrying out the process, the articles are first suitably cleaned byany conventional method, but preferably by pickling, and then thoroughly removing the pickling solution, unless phosphoric acid has been used, in which case thorough removal is not essential. The articles are then heated to a temperature nothigher than about 500 to 550 F., preferably, about 500 F., and while at this temperature, plunged into a bath of dilutedortho-phosphoric acid, allowed to remain a short time, say about a minute or two, and then taken out and transferred to a drying oven where they are then again heated to about 325to 450 F. The strength of acid that seems to give the'best results is about 33 per cent acid by weight to the balance water, though considerable variation from these proportions may be made. Repetition of the steps of treating, dipping and baking may be made if found desirable.

While the particular solution of diluted acid has been described as the preferred process, other phosphatic rust proofing solutions may be used with the preheating step to great advantage. Such phosphate solutions as those containing manganese or zinc or. iron phosphate or a mixture of these are contemplated by the above statement.

It is also contemplated that such a preheating step will be found advantageous in those treatments which provide the metal with a coating of ferroso-ferric oxid, as it seems that the preliminary heating puts the ferrous articles in a more receptive condition for action by such solutions. When, therefore, the expression rustproofing solution is used in the claims, it is intended to cover any of these active rust proofing solutions.

Now having described the invention and the preferred forms of embodiment thereof, it is We claim:

1. The process of treating articles having surfaces of ferrous metal, which comprises heating said articles to a temperature of about 500 to 550 F., immersing the heated articles in a rust-proofing solution, then removing said articles from said solution and baking at a. temperature of about 325 to 450 F.

2. The process of treating articles having surfaces of ferrous metal, which comprises heating said articles to a temperature of about 500 to 550 F., and immersing the heated articles in a phosphatic rust-proofing solution.

3. The process of treating articles having surfaces of ferrous metal, which comprises heating said articles to a temperature of about 500 to 550 F., immersing the heated articles in a phosphatic rustproofing solution, and removing said articles from said solution and baking at a temperature of about 325 to 450 F.

4. The process of treating articles having surfaces of ferrous metal, which comprises heating said articles to a temperature of about 500 to 550 F., and treating the heated articles with a solution of diluted phosphoric acid solution.

MARLIN G. BAKER. WILBERT A. DINGMAN. 

